1. Field of the Invention
This invention relates to means and methods for discriminating between friendly ground targets and those belonging to a foe whereby the inadvertent attack on a friendly target can be avoided.
More specifically, this invention relates to means carried by friendly ground targets which interact with laser target designator beams to change the character of reflected laser energy and so provide means for distinguishing between friendly targets and those belonging to a foe.
2. Description of the Related Art
Laser target designators are in common use for military systems. In such systems, a laser beam is used to illuminate a target and so designate it for attack. The laser light striking the target is reflected in all directions. A guided missile, bomb or other projectile which is directed at the target carries an internal guidance system which detects the reflected laser light and causes the missile or bomb to home in on the source of the reflected radiation.
In one version of such a system, the target is illuminated by a laser designator at a location apart from that where the missile or bomb is launched toward the target. The laser target designator may, for example, be operated by a man on the ground or in a ground vehicle or may be operated by the crew of an aircraft. A missile may be launched toward the designated target from another ground location or a missile or bomb may be launched from another attack platform such as from a second aircraft. Examples of such systems are shown by U.S. Pat. Nos. 4,143,835 and 4,259,009. In another version, the laser designator and the missile or bomb launch means are carried on the same platform; typically a helicopter or airplane.
In either case, it is the responsibility of the operator of the laser designator means to positively identify the illuminated target as belonging to the enemy. Were a friendly target to be designated by laser illumination, then a missile or a bomb launched toward the designated target would home in on that target as if it belonged to the enemy. The possibility for mistake in target identification is always present especially during nighttime and in other situations where visibility is limited.
Mistakes in target identification have occurred and, during the recent Operation Desert Storm, have resulted in casualties from friendly fire. It has been reported that, to avoid further targeting mistakes, identification devices comprising infrared beacons for attachment to ground vehicles were deployed during that operation. The beacons used battery powered infrared diodes blinking in a preset sequence which was visible to pilots and other observers using night vision devices. Such a solution was practical under the circumstances of that conflict in which absolute air superiority was quickly established and thereafter maintained. However, in other circumstances where enemy air power remained a threat, those same beacons would serve to give away vehicle locations and to mark targets for the enemy.
There remains an unfulfilled need for means to distinguish between targets which belong to friendly forces and those of the enemy upon designation of a potential target through laser illumination.